It’s been a while since AMC has had a breakout hit to match the buzz of its Breaking Bad and Mad Men era. Granted, it still has the Walking Dead franchise, but analysts are growing more and more concerned that the zombie well will eventually run dry. The problem is compounded by the fact that AMC has no corporate cushion to soften the blow: It’s not part of a larger media conglomerate like, say, Fox broadcasting was when it when it relied too heavily on American Idol a few years ago.

“AMC Networks is on the cusp of experiencing this type of chaos due to an over-reliance on TheWalking Dead and appears to have few tools, except an outright sale, to save them from further multiple compression,” media analyst Michael Nathanson wrote in a research note today.

Nathanson’s firm, MoffettNathanson, downgraded AMC’s stock from Neutral to Sell, citing ratings for Walking Dead that are “sequentially eroding at an alarming pace.”